a. Field of the Invention
This invention relates to medical devices and processes useful for the treatment of atrial arrhythmia. In particular, it relates to a preferred process and medical device used for ablation procedures in vessels of the human body, namely the pulmonary veins.
b. Background Art
Introducers and catheters have been in use for medical procedures for many years. For example, one procedure utilizes a catheter to convey an electrical stimulus to a selected location within the human body. Another procedure utilizes a catheter to monitor activity in various locations in the body for diagnostic tests. Thus, catheters may examine, diagnose and treat while positioned at specific locations within the body which are otherwise inaccessible without more invasive procedures. In use, catheters may be inserted into a major vein or artery which is near the body surface. These catheters are then guided to a specific location for examination, diagnosis and treatment by manipulating the catheter through the artery or vein of the human body, frequently with the assistance of other medical devices, such as introducers or guidewires.
One common medical procedure utilizing specialized catheters is the treatment of vessels located within the human body, frequently vessels associated with the human heart. Those procedures, most notably angioplasty procedures, utilize a catheter which often contains an inflatable balloon secured to the catheter. In some of these medical procedures, the catheter contains a pair of inflatable balloons used to limit the portion of the vessel that is treated or to assure that the catheter remains at a fixed location within the vessel throughout the medical procedure or to assist in the performance of the medical procedure.
Multiple balloon catheters are utilized throughout the body. For example, U.S. Pat. No. 5,468,239 discloses a device for circumferential laser burning of tissue in a urethral canal. This device utilizes a pair of cuffs or balloons 60 with a laser probe 12 located between those balloons. U.S. Pat. No. 5,588,961 discloses an infusion catheter for delivery of medication to a vessel and contains a pair of balloons 16, 17 and an electrode 35 secured to the catheter. Ports are provided in the catheter to introduce the medication into the space between the two balloons within the vessel. Energy may also be introduced into the electrode to encourage the movement of the medication away from the catheter toward the walls of the vessel. U.S. Pat. No. 5,256,141 discloses a pair of balloons (14, 18) with an electrode secured to a catheter to apply a controlled electric charge to material introduced into the space in the vessel between the two balloons.
Biological material may also be introduced into this space for medical treatment of the vessel. U.S. Pat. No. 5,366,490 discloses a pair of balloons 30, 32 secured to a catheter and a stylette 36. Radio frequency energy is supplied to the catheter to destroy tissue. U.S. Pat. No. 5,599,307 discloses a pair of balloons 41, 42 secured to a catheter designed to occlude a vessel. U.S. Pat. No. 5,002,532 discloses a pair of balloons 21, 22 secured to a catheter 12 for use in a dilation procedure within a vessel, whereby the two balloons may be inflated to different extents. U.S. Pat. No. 5,792,105 discloses a multichannel balloon catheter for delivering fluids which utilizes an inner and an outer balloons. See also U.S. Pat. No. 4,445,892.
In addition to the use of multiple balloons on a single catheter for medical procedures, U.S. Pat. No. 5,462,529 discloses a medical device containing a pair of catheters 12, 28, each containing a balloon 20, 48 secured at or near its distal end, which device is utilized to perform a medical procedure within a vessel. U.S. Pat. No. 5,484,412 also discloses a pair of catheters 18, 22 utilized to perform a medical procedure within a vessel, each containing an inflatable balloon 36, 38. U.S. Pat. No. 4,911,163 discloses a pair of balloons (2, 8) secured to a pair of catheters 1, 7 for introduction of medicine or diagnostic fluids into the space between the two balloons.
Atrial fibrillation is the most common sustained heart arrhythmia. It is estimated to occur in upwards of 0.4 percent of the adult population and perhaps as many as 10 percent of the population who are 60 years or older. Cox, J. L., et al., Electrophysiology, Pacing and Arrhythmia, “Operations for Atrial Fibrillation,” Clin. Cardiol. 14, 827-834 (1991).
Atrial arrhythmia may be transient or persistent. While most atrial arrhythmia occur in individuals having other forms of underlying heart disease, some atrial arrhythmia occur independently. While atrial arrhythmia do not directly cause death as frequently as ventricular arrhythmia, they increase the risk factors for a number of other diseases such as systemic and cerebral embolism and may cause a number of additional medical problems.
In the treatment of atrial arrhythmia, antiarrhythmic drugs sometimes provide relief. Other treatments for atrial arrhythmia or fibrillation involve the use of an implanted atrial defibrillator or cardioversion. See, for example, U.S. Pat. Nos. 5,282,836, 5,271,392 and 5,209,229 and Martin, D., et al., Atrial Fibrillation, pgs. 42-59 (1994).
Certain patients with symptomatic or life threatening atrial arrhythmia, however, cannot be adequately treated by drugs or these types of medical devices. Other forms of aggressive treatment are sometimes mandated, which have in the past included surgery. For example, a surgical procedure for the treatment of atrial arrhythmia known as the “Maze” procedure is discussed in Cox, J. L. et al., Electrophysiology, Pacing and Arrhythmia, “Operations for Atrial Fibrillation,” Clin. Cardiol. Vol. 14, pgs. 827-834 (1991).
Another procedure increasingly used within the last 10 to 15 years for the treatment of certain types of cardiac arrhythmia involves ablation of cardiac tissue. For example, this procedure has been commonly used to interrupt or modify existing conduction pathways associated with arrhythmia within the heart. The particular area for ablation depends on the type of underlying arrhythmia. The use of radio frequency catheter ablation for the treatment of paroxysmal atrial fibrillation is disclosed in Haissaguerre, M., et al., “Right and Left Atrial Radiofrequency Catheter Therapy of Paroxysmal Atrial Fibrillation” J. Cardiovascular Electrophsiology, V.7, pgs. 1132-1144 (December 1996). Ablation procedures have also been used for the treatment of atrioventricular (AV) nodal reentrant tachycardia. With this condition, ablation of the fast or slow AV nodal pathways has become an accepted treatment. Singer, I., et al., “Catheter Ablation for Arrhythmias” Clinical Manual of Electrophsiology, pgs. 421431 (1993); Falk, R. H., et al., Atrial Fibrillation Mechanisms in Management, pgs. 359-374 (1992); Horowitz, L. N., Current Management of Arrhythmias, pgs. 373-378 (1991); and Martin, D., et al., Atrial Fibrillation, pgs. 42-59 (1994). In addition, the use of ablation catheters for ablating locations within the heart has been disclosed, for example in U.S. Pat. Nos. 4,641,649, 5,263,493, 5,231,995, 5,228,442 and 5,281,217.
The sources of energy used for catheter ablation vary. Initially, high voltage, direct current (DC) ablation techniques were commonly used. However, because of problems associated with the use of DC current, radio frequency (RF) energy has become the preferred source of energy for ablation procedures. The use of RF energy for ablation has been disclosed, for example, in U.S. Pat. Nos. 4,945,912, 5,209,229, 5,281,218, 5,242,441, 5,246,438, 5,281,213 and 5,293,868. Other energy sources which are being used currently or are being considered for ablation of heart tissue include laser, ultrasound, microwave and fulgutronization.
Ablation of a precise location within the heart requires the precise placement of the ablation catheter within the heart. Precise positioning of the ablation catheter is especially difficult because of the physiology of the heart, particularly as the ablation procedures generally occur while the heart is beating. Commonly, the placement of the catheter is determined by a combination of electrophysiological guidance and fluoroscopy (placement of the catheter in relation to known features of the heart which are marked by radiopaque diagnostic catheters which are placed in or at known anatomical structures such as the coronary sinus, high right atrium and the right ventricle).
A process for the mapping and treatment of atrial arrhythmia using ablation catheters guided to a specific location by shaped, guiding introducers is disclosed in U.S. Pat. Nos. 5,427,119, 5,497,774, 5,575,766, 5,564,440, 5,628,316 and 5,640,955. In particular, a process for the ablation of defined tracks within the left and/or right atrium as an element of the treatment of atrial fibrillation is disclosed in U.S. Pat. No. 5,575,766.
The mechanism for initiation of some forms of atrial arrhythmia, such as atrial premature contractions, is not well understood. As a result, ablation procedures in the heart have focused on the formation of lesions within the chambers of the heart at selected locations which either prevent the passage of electrical signals associated with atrial premature contractions or prevent the formation of improper electrical pathways within the heart, which can result in atrial arrhythmia.
It has been surprisingly discovered that one source for these atrial premature contractions originates within vessels associated with the heart, in particular the pulmonary veins. Once these atrial premature contractions form in the pulmonary veins, they are periodically conducted into the left atrium. When the atrial premature contractions enter the left atrium, they can initiate or continue an episode of atrial fibrillation.
Invasive treatment of atrial fibrillation in the past around the pulmonary veins has been limited to the formation of lesions in the left atrium created by an invasive surgical procedure, such as is disclosed by Cox, J. L., et al., Electrophysiology, Pacing and Arrhythmia, “Operations for Atrial Fibrillation” Clin. Cardiol. Vol. 14, pgs. 827834 (1991). In addition, the use of precurved guiding introducers to guide ablation catheters to appropriate locations in the left atrium for use in the formation of lesions around the pulmonary veins has been disclosed in U.S. Pat. No. 5,575,766.
While these procedures have been successful in some patients, other patients require additional treatment as the treatments previously disclosed have not been completely successful in the elimination of the atrial fibrillation. In addition, these ablation procedures can be very time consuming, requiring as long as 10-15 hours.
It is therefore an aspect of this invention to disclose a medical device useful in the treatment of atrial arrhythmia, particularly atrial fibrillation.
It is an additional aspect of this invention to disclose a medical device useful for the formation of ablation lesions in vessels in the body.
It is a still further aspect of this invention to disclose a medical device containing a pair of inflatable balloons. one located inside of the other, and an ablation electrode, which components are utilized to form a circumferential ablation lesion for the treatment of atrial arrhythmia, particularly atrial premature contractions.
It is a still further aspect of this invention to disclose a process for the formation of circumferential ablation lesions in vessels in the human body.
It is a still further aspect of this invention to disclose a process for ablation of tissue located within the pulmonary veins, or on the os of the pulmonary veins.
It is a still further aspect of this invention to disclose a process for the formation of circumferential lesions in the pulmonary veins, or on the os of the pulmonary veins.
It is a still further aspect of this invention to disclose medical procedures for the production of circumferential ablation lesions within vessels of the heart, or on the os of those vessels, for the treatment of atrial fibrillation.
It is a still further aspect of this invention to disclose a process for the formation of ablation lesions within a vessel of the heart, or on the os of that vessel, using RF energy.
These and other aspects of the invention are disclosed by the processes for the treatment of atrial arrhythmia and the design of the medical products for use with those processes.